The present invention relates to machine tooled diaphragm partitions or nozzles for steam turbines and particularly relates to diaphragm partitions and nozzles which are readily manufactured and installed at reduced costs as original equipment manufacture or repairs.
Diaphragms for nozzle stages in steam turbines typically comprise a plurality of circumferentially spaced partitions secured at opposite ends to inner and outer spacer bands or rings. The inner and outer spacer bands are secured to an inner web and an outer ring, respectively. In original equipment manufacture, the partitions are welded into the inner and outer bands, and the bands are welded to the web and ring, respectively. The welding processes are labor intensive, require skilled artisans, are costly and time consuming. Moreover, the welding processes and the welds introduce substantial distortions into the diaphragm.
For effecting repairs, partial partition coupon segments are generally welded into place with remaining portions of the partitions. Because the base materials are high strength alloys, pre- and post-heat treating processes are necessary. This stress relief process elevates the temperature and magnifies the distortion of the steam path. When all of the thermal processes are completed, each partition is then bent and shaped mechanically to an acceptable attitude with all nozzle areas between partitions being made approximately equal. Accordingly, there is a need for a partition and diaphragm construction which will decrease the cycle time and cost of original or repaired diaphragms while improving the quality of the assembled product.